Gallium-mercury interfacial tension

The balance of the results depends on calculation of contact angles from measurements of capillary rise [10]. A value of 41 dynes per cm. for the gallium-mercury interfacial tension, determined in previous work in this laboratory [8], was used in these calculations. The densities of the two saturated phases are 6.28 grams per cc. for the gallium and 13.35 for the mercury [8]. 

An approximate value of the interfacial tension between gallium and mercury was obtained, which agreed within experimental error with a much more accurate measurement made previously in this laboratory. 

For liquid metals (mercury, gallium) or their alloys, one can measure another interfacial quantity, interfacial tension equal to the specific energy of the interface formation, y, at different values of the electrode potential, E[, 17]. At equilibrium the Lippmann equation relates it to the electrode-charge density a, that is, to the charge Q in Eq. (2) per unit surface area ... 

Of special interest is the case of contact between solid and liquid metals of similar chemical nature, such as zinc and mercury and aluminum and gallium. In these cases, the work of adhesion between the solid and liquid phases remains high, but the interfacial tension, Ojl, may be very low, reaching about 10% of Ojc. Such lowering in the interfacial tension is the reason for liquid-metal embrittlement, which is discussed in detail in Chapter 7. 

Experimentally, the electrical double-layer affect is manifest in the phenomenon named electrocapillarity. The phenomenon has been studied for many years, and there exist thermodynamic relationships that relate interfacial surface tension between electrode and electrolyte solution to the structure of the double layer. Typically the metal used for these measurements is mercury since it is the only conveniently available metal that is liquid at room temperature (although some work has been carried out with gallium. Wood s metal, and lead at elevated temperature). 

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